The Northern Uí Néill was any of several dynasties in north-western medieval Ireland that claimed descent from a common ancestor, Niall of the Nine Hostages. Other dynasties in central and eastern Ireland who also claimed descent from Niall are termed the Southern Uí Néill. The dynasties of the Northern Uí Néill were the Cenél Conaill and Cenél nEógain, named after the two most powerful sons of Niall: Conall and Eógain.

Ulster is one of the four traditional or historic Irish provinces. It is made up of nine counties: six of these constitute Northern Ireland ; the remaining three are in the Republic of Ireland.